Insulating composition for impregnating electrical tape



Patented June 11, 1935 INSULATING:

COMPOSITION FOR IMPREG- v NATING'ELECTRICAL TAPE A Frankl. Clark-andRalph A. RusdettaQPittsfield,

I No *Drawing.

Mesa, vassignors to General Electric Company,

' fl Claims. (01. 106- 1 7) g I temperature maintained at about C.forab'out i "The present invention relates broadly toelectricarinsulation'. More specifically this invention isconcerned witha new and improved tape adapted for use in electrical "apparatus; aprocess forpreparing the same, and the composition em- ..p'loyedzinthe-emanufacture. of said tape.

- JFr ictiontape. is employedv 'in' electrical apparatus, as forexample; in motor, 'armatures. ,Qrdinary tape, heretofore employed hasbeen disadvantageous. especially in connection With motorarmature;application, in that it prevented the proper curing of the insulatingvarnish applied 'to the coils after the tape was applied. This hasprobably been due to the fact that ordinary friction tapes containrubber compounds therein which prevent the solvent in the varnish fromescaping when the coil is baked. It is, of course, obvious that suchsolvent must be entirely eliminated and the varnish properly curedbefore the coil is satisfactory.

We have. discovered that we can produce a friction tape adapted for usewherever such a tape is now used and where subsequent to the applicationof .said tape a varnish is applied and baking operations carried out.The friction tape of our invention can be manufactured not only at acheaper cost than present tapes but is of such a nature that iteliminates the objectionable features mentioned above and permits theproper curing and satisfactory production of apparatus in which it isused.

In order that our invention may be more fully understood the followingdetailed description thereof is given and its scope pointed out in theappended claims.

In manufacturing the tape a .novel composition is employed which impartsthe desirable characteristics to the tape. We employ a treatingcomposition for producing such tape, composed of a high melting wax suchas Montan Wax; colophony (rosin) or derivatives thereof, such as estergum; and a non-drying, fatty oil, such as castor oil. While theproportions of the ingredients in the composition may be variedconsiderably, a typical composition for use contains substantially Percent by Weight Montan wax 40 Rosin 32 Castor oil 28 .sirablecharacteristics.

35 minutes. The rosin is used largely to maintain viscosity value.At-t-he end of this time: the castor oil isadded, this ingredient beingvemployed in order to promote plasticity andto act as a- .flux for therosin and (the mineral .wax or other wax-employed. The temperature ofthe mass is maintained not higher than 150? 0., and the mixture is keptwell stirred and; is heated for I about 1%; hours. The characteristicsofthis' particular compound are asfollows: H 1

'Vi'scosityn'la 70 centipoise-'at '1'00 C. measured with the MacMichaelviscosimeter Flash 243 C. Burn 278 C. Flow point approximately- 60 C.

The tape which is treated with this material can be any of thecommercial types of fibrous material employed as tape. The width may beof any convenient dimension depending on they use to which the tape isput. In treating the tape the composition obtained as described above isheated in air to a temperature of about C. The tape in any convenientform, for example as rolls, is immersed in the composition and thetemperature maintained at about 165- C. for

about two hours. Care must betaken to see that the tape is entirelyimmersed in' the treating composition during this time. At the end ofthis treatment the tape is removed from the composition, allowed todrain and cool to room temperathat castor oil is merely typical of anynon-drying oil which may be employed. 7

The proportions of the various ingredients em:

ployed may be varied considerably. The particuv lar mixture cited in theexample has been found desirable since it gives the degree of tackinessdesired in the tape without sacrifice in other de- As illustrative ofthe fact that the proportions of the ingredients entering into thetreating composition may be varied we cite the following compositionwhich may also be successfully employed:

- Percent Montan wax Rosin 40 Castor oil 10 In this example, well as inthe first example,

the proportion 'of Montan wax preponderates over each of the otheringredients.

While the specific example illustrating "the" treatment of the rolls inthe treatingcomposition calls for a temperature of about 165- "C. thistem-- perature is not fixed but may be varied depending on the timetaken in the treating operations.

For example, a temperature of about 150 C. may be employed when the tapeis immersed in the composition, the time of treatment being lengthenedcorrespondingly. Where the tape rolls are kept immersed at about 165 C.for about'two; hours, at about 150 C. the time would be increased toabout two to four hours. V What we claim as newand desire-to secure byamounts both] of rosin and non-drying fatty oil to produce an adhesivematerial suitable for use in insulating friction tape.

2. An insulating composition 'a preponderant amount of Montan wax, andsubstantial amounts of rosin, and castor oil to prowhich consists ofduce a tacky material having a flow point ofapproximately C.

3. A composition for treating fibrous material to form an electricaltape which consists of sub stantially 40% by weight of Montan wax, 32%by weight of rosin, and 28% by weight of castor oil.

4. A composition having a flow point of about 60 C. comprising a mixtureby weight of about 40 to 50 per cent of Montan wax, about 32 to 40 percent of rosin, and about 28 to 10 per cent of 0351301011; h

5. A composition of matter containing a high melting wax in an amount atleast about 40 per cent by weight and also containing suflicientamounts-both of rosin and castor oil to produce a tacky, solid materialsuitable for use in insu- ..lating friction tape.

6. ,A composition of matter suitable for electrical insulating usecomprising a mixture by weight of about 40 to 50 per cent of highmelting wax, about 32 to 40 per cent of .a material containing abieticacid radical, andabout 28 to 10 per cent of castor oil. 1

,7. A composition of matter suitable for electric insulat-inguseconsisting of a mixtureby-weight of about 40 to 50 per cent of a memberof the class consisting of Montan wax, carnauba wax and ozokerite, about32 to 40 per cent of rosin and about 28 to 10 per cent of castor oil.

' FRANK'M. CLARK.

RALPH A. RUSCETTA.

